package whf.framework.util.images;

/** 

 * PngEncoder takes a Java Image object and creates a byte string which can be saved as a PNG file. 

 * The Image is presumed to use the DirectColorModel. 

 * 

 * Thanks to Jay Denny at KeyPoint Software 

 * http://www.keypoint.com/ 

 * who let me develop this code on company time. 

 * 

 * You may contact me with (probably very-much-needed) improvements, 

 * comments, and bug fixes at: 

 * 

 * david@catcode.com 

 * 

 * This library is free software; you can redistribute it and/or 

 * modify it under the terms of the GNU Lesser General Public 

 * License as published by the Free Software Foundation; either 

 * version 2.1 of the License, or (at your option) any later version. 

 *  

 * This library is distributed in the hope that it will be useful, 

 * but WITHOUT ANY WARRANTY; without even the implied warranty of 

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 

 * Lesser General Public License for more details. 

 *  

 * You should have received a copy of the GNU Lesser General Public 

 * License along with this library; if not, write to the Free Software 

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 

 * A copy of the GNU LGPL may be found at 

 * http://www.gnu.org/copyleft/lesser.html, 

 * 

 * @author J. David Eisenberg 

 * @version 1.4, 31 March 2000 

 */

import java.awt.Image;
import java.awt.image.ImageObserver;
import java.awt.image.PixelGrabber;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.CRC32;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;

public class PngEncoder extends Object{

	/** Constant specifying that alpha channel should be encoded. */

	public static final boolean ENCODE_ALPHA = true;

	/** Constant specifying that alpha channel should not be encoded. */

	public static final boolean NO_ALPHA = false;

	/** Constants for filters */

	public static final int FILTER_NONE = 0;

	public static final int FILTER_SUB = 1;

	public static final int FILTER_UP = 2;

	public static final int FILTER_LAST = 2;

	protected byte[] pngBytes;

	protected byte[] priorRow;

	protected byte[] leftBytes;

	protected Image image;

	protected int width, height;

	protected int bytePos, maxPos;

	protected int hdrPos, dataPos, endPos;

	protected CRC32 crc = new CRC32();

	protected long crcValue;

	protected boolean encodeAlpha;

	protected int filter;

	protected int bytesPerPixel;

	protected int compressionLevel;

	/**
	 * 
	 * Class constructor
	 * 
	 * 
	 * 
	 */

	public PngEncoder()	{
		this(null, false, FILTER_NONE, 0);
	}

	/**
	 * 
	 * Class constructor specifying Image to encode, with no alpha channel
	 * encoding.
	 * 
	 * 
	 * 
	 * @param image
	 *            A Java Image object which uses the DirectColorModel
	 * 
	 * @see java.awt.Image
	 * 
	 */

	public PngEncoder(Image image)	{
		this(image, false, FILTER_NONE, 0);
	}

	/**
	 * 
	 * Class constructor specifying Image to encode, and whether to encode
	 * alpha.
	 * 
	 * 
	 * 
	 * @param image A Java Image object which uses the DirectColorModel
	 * 
	 * @param encodeAlpha Encode the alpha channel? false=no; true=yes
	 * 
	 * @see java.awt.Image
	 * 
	 */

	public PngEncoder(Image image, boolean encodeAlpha)	{
		this(image, encodeAlpha, FILTER_NONE, 0);
	}

	/**
	 * 
	 * Class constructor specifying Image to encode, whether to encode alpha,
	 * and filter to use.
	 * 
	 * 
	 * 
	 * @param image A Java Image object which uses the DirectColorModel
	 * 
	 * @param encodeAlpha Encode the alpha channel? false=no; true=yes
	 * 
	 * @param whichFilter 0=none, 1=sub, 2=up
	 * 
	 * @see java.awt.Image
	 * 
	 */

	public PngEncoder(Image image, boolean encodeAlpha, int whichFilter){
		this(image, encodeAlpha, whichFilter, 0);
	}

	/**
	 * 
	 * Class constructor specifying Image source to encode, whether to encode
	 * alpha, filter to use, and compression level.
	 * 
	 * 
	 * 
	 * @param image A Java Image object
	 * 
	 * @param encodeAlpha Encode the alpha channel? false=no; true=yes
	 * 
	 * @param whichFilter  0=none, 1=sub, 2=up
	 * 
	 * @param compLevel 0..9
	 * 
	 * @see java.awt.Image
	 * 
	 */

	public PngEncoder(Image image, boolean encodeAlpha, int whichFilter, int compLevel)	{

		this.image = image;

		this.encodeAlpha = encodeAlpha;

		setFilter(whichFilter);

		if (compLevel >= 0 && compLevel <= 9)
		{

			this.compressionLevel = compLevel;

		}

	}

	/**
	 * 
	 * Set the image to be encoded
	 * 
	 * 
	 * 
	 * @param image
	 *            A Java Image object which uses the DirectColorModel
	 * 
	 * @see java.awt.Image
	 * 
	 * @see java.awt.image.DirectColorModel
	 * 
	 */

	public void setImage(Image image)
	{

		this.image = image;

		pngBytes = null;

	}

	/**
	 * 
	 * Creates an array of bytes that is the PNG equivalent of the current
	 * image, specifying whether to encode alpha or not.
	 * 
	 * 
	 * 
	 * @param encodeAlpha
	 *            boolean false=no alpha, true=encode alpha
	 * 
	 * @return an array of bytes, or null if there was a problem
	 * 
	 */

	public byte[] pngEncode(boolean encodeAlpha)
	{

		byte[] pngIdBytes = { -119, 80, 78, 71, 13, 10, 26, 10 };

		if (image == null)

		{

			return null;

		}

		width = image.getWidth(null);

		height = image.getHeight(null);

//		this.image = image;

		/*
		 * 
		 * start with an array that is big enough to hold all the pixels
		 * 
		 * (plus filter bytes), and an extra 200 bytes for header info
		 * 
		 */

		pngBytes = new byte[((width + 1) * height * 3) + 200];

		/*
		 * 
		 * keep track of largest byte written to the array
		 * 
		 */

		maxPos = 0;

		bytePos = writeBytes(pngIdBytes, 0);

		hdrPos = bytePos;

		writeHeader();

		dataPos = bytePos;

		if (writeImageData())
		{

			writeEnd();

			pngBytes = resizeByteArray(pngBytes, maxPos);

		}
		else
		{

			pngBytes = null;

		}

		return pngBytes;

	}

	/**
	 * 
	 * Creates an array of bytes that is the PNG equivalent of the current
	 * image.
	 * 
	 * Alpha encoding is determined by its setting in the constructor.
	 * 
	 * 
	 * 
	 * @return an array of bytes, or null if there was a problem
	 * 
	 */

	public byte[] pngEncode()
	{

		return pngEncode(encodeAlpha);

	}

	/**
	 * 
	 * Set the alpha encoding on or off.
	 * 
	 * 
	 * 
	 * @param encodeAlpha
	 *            false=no, true=yes
	 * 
	 */

	public void setEncodeAlpha(boolean encodeAlpha)	{
		this.encodeAlpha = encodeAlpha;
	}

	/**
	 * 
	 * Retrieve alpha encoding status.
	 * 
	 * 
	 * 
	 * @return boolean false=no, true=yes
	 * 
	 */

	public boolean getEncodeAlpha()	{
		return encodeAlpha;
	}

	/**
	 * 
	 * Set the filter to use
	 * 
	 * 
	 * 
	 * @param whichFilter
	 *            from constant list
	 * 
	 */

	public void setFilter(int whichFilter)
	{

		this.filter = FILTER_NONE;

		if (whichFilter <= FILTER_LAST)
		{

			this.filter = whichFilter;

		}

	}

	/**
	 * 
	 * Retrieve filtering scheme
	 * 
	 * 
	 * 
	 * @return int (see constant list)
	 * 
	 */

	public int getFilter()
	{

		return filter;

	}

	/**
	 * 
	 * Set the compression level to use
	 * 
	 * 
	 * 
	 * @param level
	 *            0 through 9
	 * 
	 */

	public void setCompressionLevel(int level)
	{

		if (level >= 0 && level <= 9)
		{

			this.compressionLevel = level;

		}

	}

	/**
	 * 
	 * Retrieve compression level
	 * 
	 * 
	 * 
	 * @return int in range 0-9
	 * 
	 */

	public int getCompressionLevel()
	{

		return compressionLevel;

	}

	/**
	 * 
	 * Increase or decrease the length of a byte array.
	 * 
	 * 
	 * 
	 * @param array
	 *            The original array.
	 * 
	 * @param newLength
	 *            The length you wish the new array to have.
	 * 
	 * @return Array of newly desired length. If shorter than the
	 * 
	 * original, the trailing elements are truncated.
	 * 
	 */

	protected byte[] resizeByteArray(byte[] array, int newLength)
	{

		byte[] newArray = new byte[newLength];

		int oldLength = array.length;

		System.arraycopy(array, 0, newArray, 0,

		Math.min(oldLength, newLength));

		return newArray;

	}

	/**
	 * 
	 * Write an array of bytes into the pngBytes array.
	 * 
	 * Note: This routine has the side effect of updating
	 * 
	 * maxPos, the largest element written in the array.
	 * 
	 * The array is resized by 1000 bytes or the length
	 * 
	 * of the data to be written, whichever is larger.
	 * 
	 * 
	 * 
	 * @param data
	 *            The data to be written into pngBytes.
	 * 
	 * @param offset
	 *            The starting point to write to.
	 * 
	 * @return The next place to be written to in the pngBytes array.
	 * 
	 */

	protected int writeBytes(byte[] data, int offset)
	{

		maxPos = Math.max(maxPos, offset + data.length);

		if (data.length + offset > pngBytes.length)
		{

			pngBytes = resizeByteArray(pngBytes, pngBytes.length +

			Math.max(1000, data.length));

		}

		System.arraycopy(data, 0, pngBytes, offset, data.length);

		return offset + data.length;

	}

	/**
	 * 
	 * Write an array of bytes into the pngBytes array, specifying number of
	 * bytes to write.
	 * 
	 * Note: This routine has the side effect of updating
	 * 
	 * maxPos, the largest element written in the array.
	 * 
	 * The array is resized by 1000 bytes or the length
	 * 
	 * of the data to be written, whichever is larger.
	 * 
	 * 
	 * 
	 * @param data
	 *            The data to be written into pngBytes.
	 * 
	 * @param nBytes
	 *            The number of bytes to be written.
	 * 
	 * @param offset
	 *            The starting point to write to.
	 * 
	 * @return The next place to be written to in the pngBytes array.
	 * 
	 */

	protected int writeBytes(byte[] data, int nBytes, int offset)
	{

		maxPos = Math.max(maxPos, offset + nBytes);

		if (nBytes + offset > pngBytes.length)
		{

			pngBytes = resizeByteArray(pngBytes, pngBytes.length +

			Math.max(1000, nBytes));

		}

		System.arraycopy(data, 0, pngBytes, offset, nBytes);

		return offset + nBytes;

	}

	/**
	 * 
	 * Write a two-byte integer into the pngBytes array at a given position.
	 * 
	 * 
	 * 
	 * @param n
	 *            The integer to be written into pngBytes.
	 * 
	 * @param offset
	 *            The starting point to write to.
	 * 
	 * @return The next place to be written to in the pngBytes array.
	 * 
	 */

	protected int writeInt2(int n, int offset)
	{

		byte[] temp = { (byte) ((n >> 8) & 0xff),

		(byte) (n & 0xff) };

		return writeBytes(temp, offset);

	}

	/**
	 * 
	 * Write a four-byte integer into the pngBytes array at a given position.
	 * 
	 * 
	 * 
	 * @param n
	 *            The integer to be written into pngBytes.
	 * 
	 * @param offset
	 *            The starting point to write to.
	 * 
	 * @return The next place to be written to in the pngBytes array.
	 * 
	 */

	protected int writeInt4(int n, int offset)
	{

		byte[] temp = { (byte) ((n >> 24) & 0xff),

		(byte) ((n >> 16) & 0xff),

		(byte) ((n >> 8) & 0xff),

		(byte) (n & 0xff) };

		return writeBytes(temp, offset);

	}

	/**
	 * 
	 * Write a single byte into the pngBytes array at a given position.
	 * 
	 * 
	 * 
	 * @param n
	 *            The integer to be written into pngBytes.
	 * 
	 * @param offset
	 *            The starting point to write to.
	 * 
	 * @return The next place to be written to in the pngBytes array.
	 * 
	 */

	protected int writeByte(int b, int offset)
	{

		byte[] temp = { (byte) b };

		return writeBytes(temp, offset);

	}

	/**
	 * 
	 * Write a string into the pngBytes array at a given position.
	 * 
	 * This uses the getBytes method, so the encoding used will
	 * 
	 * be its default.
	 * 
	 * 
	 * 
	 * @param n
	 *            The integer to be written into pngBytes.
	 * 
	 * @param offset
	 *            The starting point to write to.
	 * 
	 * @return The next place to be written to in the pngBytes array.
	 * 
	 * @see java.lang.String#getBytes()
	 * 
	 */

	protected int writeString(String s, int offset)
	{

		return writeBytes(s.getBytes(), offset);

	}

	/**
	 * 
	 * Write a PNG "IHDR" chunk into the pngBytes array.
	 * 
	 */

	protected void writeHeader()
	{

		int startPos;

		startPos = bytePos = writeInt4(13, bytePos);

		bytePos = writeString("IHDR", bytePos);

		width = image.getWidth(null);

		height = image.getHeight(null);

		bytePos = writeInt4(width, bytePos);

		bytePos = writeInt4(height, bytePos);

		bytePos = writeByte(8, bytePos); // bit depth

		bytePos = writeByte((encodeAlpha) ? 6 : 2, bytePos); // direct model

		bytePos = writeByte(0, bytePos); // compression method

		bytePos = writeByte(0, bytePos); // filter method

		bytePos = writeByte(0, bytePos); // no interlace

		crc.reset();

		crc.update(pngBytes, startPos, bytePos - startPos);

		crcValue = crc.getValue();

		bytePos = writeInt4((int) crcValue, bytePos);

	}

	/**
	 * 
	 * Perform "sub" filtering on the given row.
	 * 
	 * Uses temporary array leftBytes to store the original values
	 * 
	 * of the previous pixels. The array is 16 bytes long, which
	 * 
	 * will easily hold two-byte samples plus two-byte alpha.
	 * 
	 * 
	 * 
	 * @param pixels
	 *            The array holding the scan lines being built
	 * 
	 * @param startPos
	 *            Starting position within pixels of bytes to be filtered.
	 * 
	 * @param width
	 *            Width of a scanline in pixels.
	 * 
	 */

	protected void filterSub(byte[] pixels, int startPos, int width)
	{

		int i;

		int offset = bytesPerPixel;

		int actualStart = startPos + offset;

		int nBytes = width * bytesPerPixel;

		int leftInsert = offset;

		int leftExtract = 0;

		for (i = actualStart; i < startPos + nBytes; i++)
		{

			leftBytes[leftInsert] = pixels[i];

			pixels[i] = (byte) ((pixels[i] - leftBytes[leftExtract]) % 256);

			leftInsert = (leftInsert + 1) % 0x0f;

			leftExtract = (leftExtract + 1) % 0x0f;

		}

	}

	/**
	 * 
	 * Perform "up" filtering on the given row.
	 * 
	 * Side effect: refills the prior row with current row
	 * 
	 * 
	 * 
	 * @param pixels
	 *            The array holding the scan lines being built
	 * 
	 * @param startPos
	 *            Starting position within pixels of bytes to be filtered.
	 * 
	 * @param width
	 *            Width of a scanline in pixels.
	 * 
	 */

	protected void filterUp(byte[] pixels, int startPos, int width)
	{

		int i, nBytes;

		byte current_byte;

		nBytes = width * bytesPerPixel;

		for (i = 0; i < nBytes; i++)
		{

			current_byte = pixels[startPos + i];

			pixels[startPos + i] = (byte) ((pixels[startPos + i] - priorRow[i]) % 256);

			priorRow[i] = current_byte;

		}

	}

	/**
	 * 
	 * Write the image data into the pngBytes array.
	 * 
	 * This will write one or more PNG "IDAT" chunks. In order
	 * 
	 * to conserve memory, this method grabs as many rows as will
	 * 
	 * fit into 32K bytes, or the whole image; whichever is less.
	 * 
	 * 
	 * 
	 * 
	 * 
	 * @return true if no errors; false if error grabbing pixels
	 * 
	 */

	protected boolean writeImageData()
	{

		int rowsLeft = height; // number of rows remaining to write

		int startRow = 0; // starting row to process this time through

		int nRows; // how many rows to grab at a time

		byte[] scanLines; // the scan lines to be compressed

		int scanPos; // where we are in the scan lines

		int startPos; // where this line’s actual pixels start (used for
						// filtering)

		byte[] compressedLines; // the resultant compressed lines

		int nCompressed; // how big is the compressed area?

//		int depth; // color depth ( handle only 8 or 32 )

		PixelGrabber pg;

		bytesPerPixel = (encodeAlpha) ? 4 : 3;

		Deflater scrunch = new Deflater(compressionLevel);

		ByteArrayOutputStream outBytes =

		new ByteArrayOutputStream(1024);

		DeflaterOutputStream compBytes = new DeflaterOutputStream(outBytes,
				scrunch);

		try
		{

			while (rowsLeft > 0)
			{

				nRows = Math.min(32767 / (width * (bytesPerPixel + 1)),
						rowsLeft);

				// nRows = rowsLeft;

				int[] pixels = new int[width * nRows];

				pg = new PixelGrabber(image, 0, startRow,

				width, nRows, pixels, 0, width);

				try {

					pg.grabPixels();

				} catch (Exception e) {

					System.err.println("interrupted waiting for pixels!");

					return false;

				}

				if ((pg.getStatus() & ImageObserver.ABORT) != 0) {

					System.err.println("image fetch aborted or errored");

					return false;

				}

				/*
				 * 
				 * Create a data chunk. scanLines adds "nRows" for
				 * 
				 * the filter bytes.
				 * 
				 */

				scanLines = new byte[width * nRows * bytesPerPixel + nRows];

				if (filter == FILTER_SUB)
				{

					leftBytes = new byte[16];

				}

				if (filter == FILTER_UP)
				{

					priorRow = new byte[width * bytesPerPixel];

				}

				scanPos = 0;

				startPos = 1;
				
				for (int i = 0; i < pixels.length; i++) {
					if (i % width == 0)
					{

						scanLines[scanPos++] = (byte) filter;

						startPos = scanPos;

					}

					scanLines[scanPos++] = (byte) ((pixels[i] >> 16) & 0xff);

					scanLines[scanPos++] = (byte) ((pixels[i] >> 8) & 0xff);

					scanLines[scanPos++] = (byte) ((pixels[i]) & 0xff);

					if (encodeAlpha)
					{

						scanLines[scanPos++] = (byte) ((pixels[i] >> 24) & 0xff);

					}

					if ((i % width == width - 1) && (filter != FILTER_NONE))
					{

						if (filter == FILTER_SUB)

						{

							filterSub(scanLines, startPos, width);

						}

						if (filter == FILTER_UP)

						{

							filterUp(scanLines, startPos, width);

						}

					}

				}

				/*
				 * 
				 * Write these lines to the output area
				 * 
				 */

				compBytes.write(scanLines, 0, scanPos);

				startRow += nRows;

				rowsLeft -= nRows;

			}

			compBytes.close();

			/*
			 * 
			 * Write the compressed bytes
			 * 
			 */

			compressedLines = outBytes.toByteArray();

			nCompressed = compressedLines.length;

			crc.reset();

			bytePos = writeInt4(nCompressed, bytePos);

			bytePos = writeString("IDAT", bytePos);

			crc.update("IDAT".getBytes());

			bytePos = writeBytes(compressedLines, nCompressed, bytePos);

			crc.update(compressedLines, 0, nCompressed);

			crcValue = crc.getValue();

			bytePos = writeInt4((int) crcValue, bytePos);

			scrunch.finish();

			return true;

		}

		catch (IOException e) {

			System.err.println(e.toString());

			return false;

		}

	}

	/**
	 * 
	 * Write a PNG "IEND" chunk into the pngBytes array.
	 * 
	 */

	protected void writeEnd()

	{

		bytePos = writeInt4(0, bytePos);

		bytePos = writeString("IEND", bytePos);

		crc.reset();

		crc.update("IEND".getBytes());

		crcValue = crc.getValue();

		bytePos = writeInt4((int) crcValue, bytePos);

	}

}